Technical Abstract:
National nutrient databases rely, in part, on the generation of original analytical data to estimate nutrient values for commonly consumed foods. The generation of representative analytical values for nutritional components requires the development of a sampling plan which includes both the demographic plan and a strategy for the collection of units (e.g., packages of cereal, heads of cabbage) of a food. The demographic plan defines the geographic locations for sampling as well as the type (e.g., retail, wholesale, field) of outlets where the sample units will be selected. The description of the food (e.g., commodity, formulation) will impact the type of sample units to select and the number of units required. The plan should include consideration of multiple factors (e.g., brand, climate, ripeness, processing treatments) which have an impact on the mean and statistical variability of values for a given food and component. USDA's National Food and Nutrient Analysis Program includes research on food sampling to determine the optimal sampling scheme for each food. A probability-based multi-stage sampling strategy has been developed to assure the representativeness of food samples collected. Sampling plans for more than 1000 agricultural products (e.g., fruits, vegetables, meats, flours) and processed foods (e.g., pizza, macaroni and cheese) have been developed. Basic statistical concepts of sampling will be discussed and will be demonstrated by developing sampling plans for four foods (poultry, bread, margarine, and one processed product) with application to developed and developing countries.